SACRAMENTO, Calif.— A new legal agreement between conservation groups and the U.S. Forest Service requires the agency to fully assess the impacts of snowmobiles on wildlife, plants and quiet recreation in five California national forests — the Stanislaus, Eldorado, Tahoe, Plumas and Lassen — within the next two years.

The agreement settles a lawsuit that challenged the Forest Service’s practice of avoiding detailed environmental review on these national forests in the central and northern Sierra and southern Cascades by issuing “categorical exclusions” – decisions that avoid environmental review – and relying on outdated environmental studies for its snowmobile trail-grooming program in California.

Snowmobiles are extremely noisy and polluting. The Environmental Protection Agency found in 2002 that one snowmobile can emit nearly as much pollution as 100 passenger cars; and in 2008, a report by the Congressional Research Service found that in one hour, a new-model snowmobile emits as much hydrocarbon as a 2008 model automobile emits in about four years — 54,000 miles — of driving. Snow compaction, noise and related stress can do serious harm to wildlife.

“We’re delighted that the Forest Service has finally agreed to take a hard look at the impacts of snowmobiles on wildlife in the winter months,” said Lisa Belenky, a senior attorney with the Center for Biological Diversity. “The harm that snowmobiles do to Sierra Nevada red foxes, Pacific fishers and mountain lions urgently needs to be studied.”

Conservationists believe the Forest Service also needs to consider providing greater protections from snowmobiles for rare plants, riparian areas, wetland habitats and at stream crossings; the impacts to under-snow vegetation and soils can be devastating if riding is allowed when snows are too shallow.

In addition to pollution, studies show that snowmobiles harass wildlife, causing increased physiological stress responses in winter months when many animals are already vulnerable from low temperatures, inclement weather and reduced food supply. Chronic stress can inhibit reproduction and cause other health problems. The vehicles can also cause disruption in wildlife movement patterns, making it more difficult for animals to find reliable food sources.

The Center for Biological Diversity, Snowlands Network and Winter Wildlands Alliance were all co-plaintiffs in this litigation and participated in the settlement. Advocates for the West’s attorney Laurie Rule represented them in this lawsuit.

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 625,000 members and online activists dedicated to the protection of endangered species and wild places.